Search PubMed⌕ Search

Biomedical subjects

J D Owen

Publications and source records attributed to J D Owen.

11 recordsLinked to original sources
PubMed1977

North-east Essex perinatal mortality survey--1971 to 1975.

A method of carrying out a Perinatal Mortality Survey in a non-academic district obstetric service is described. The results show a trend of improving perinatal mortality and the various factors that may be influencing this trend are discussed.

Birth Weight↗
PubMed1976

Computer-simulated urea reflection coefficients in human red cells.

Relative volume curves for human red cells were generated with a computer program to simulate the experimental results obtained by rapidly mixing red cells and urea. Known values for the permeability variables were used in the Kedem and Katchalsky (Biochim. Biophys. Acta (1958) 27, 229-246) solute and solvent flux equations. The different values used for the reflection coefficient, o, were 0.62, 0.75 and 1.0. The theoretical computer curves with o = 0.75 compared closely with the experimental stopped-flow curves.

Cell Membrane Permeability↗
PubMed1976

Reflection coefficients of permeant nonelectrolytes for dog and beef red cell membranes.

The reflection coefficient, sigma, for several small permeant nonelectrolytes was determined for dog and beef red blood cell membranes. Our sigma values were considerably higher than those previously reported for dog cells; e.g., out sigma urea was 87% higher than the sigma urea of Rich, Sha'afi, Barton and Solomon (J. Gen. Physiol. 50: 2391, 1967). Our sigma values for urea were only slightly greater in beef cells than previously reported by Farmer and Macey (Biochim. Biophys. Acta 290: 290, 1972). We found that a trend exists when (1 - sigma) is plotted against the log of the permeability coefficient, omega. This observation is also consistent with our previously reported sigma data for human red cell membranes (Owen & Eyring, J. Gen. Physiol. 66: 241, 1972). This trend suggests that small hydrophilic molecules interact highly with cell membrane water. The exceptions to this trend were lipophilic molecules, indicating they do not interact with water while penetrating the red cell membrane.

Acetamides↗
PubMed1975

Reflection coefficients of permeant molecules in human red cell suspensions.

The Staverman reflection coefficient, sigma for several permeant molecules was determined in human red cell suspensions with a Durrum stopped-flow spectrophotometer. This procedure was first used with dog, cat, and beef red cells and with human red cells. The stopped-flow technique used was similar to the rapid-flow method used by those who originally reported sigma measurements in human red cells for molecules which rapidly penetrate the red cell membrane. The sigma values we obtained agreed with those previously reported for most of the slow penetrants, except malonamide, but disagreed with all the sigma values previously reported for the rapid penetrants. We were unable to calculate an "equivalent pore radius" with our sigma data. The advantages of our equipment and our experimental procedure are discussed. Our sigma data suggest that sigma is indirectly proportional to the log of the nonelectrolyte permeability coefficient, omega. Since a similar trend has been previously shown for log omega and molar volume of the permeant molecules, a correlatioo was shown between sigma and molar volume suggesting the membrane acts as a sieve.

Cell Membrane Permeability↗